1. Field of the Invention
The present invention relates to the toothing system of a gearwheel having a plurality of teeth whose tooth flanks have involute form above a tooth-root region of the tooth flanks, wherein the tooth-root region of the tooth flanks that, as viewed in normal section, extends between a root useful point and a root point has elliptical shape, tangentially adjoins the involute region of the tooth flank at the root useful point and tangentially contacts the root circle at the root point. The present invention also relates to a gearwheel having a corresponding toothing system as well as to a gearwheel pair comprising two such gearwheels.
2. Description of the Related Art
Such toothing systems and gearwheels having elliptical tooth-root fillet are known from the prior art.
From DE 10208408 A1 there is additionally known a non-involute toothing system for the impeller of a gear pump, in which the meshing tooth tips and tooth roots of the teeth are formed by elliptical curves that merge into one another. In this way it is provided in particular that the mutually facing tooth flanks of two neighboring teeth, as viewed in normal section, are formed in their tooth-root region by a common partial section of an ellipse, whose minor semiaxis lies within the symmetry plane—formed by the radial through the root point—through the tooth space.
A further pump toothing system is known from U.S. Pat. No. 2,389,728, which system has an annular gear with internal toothing and an internal gearwheel running eccentrically within the internal toothing of the annular gear. In this case the flank profile of the teeth of the internal toothing of the external annulus is defined in the tooth-tip region by an ellipse. The geometry of the toothing of the internal gearwheel is then calculated from the toothing equation. To favor one running direction of the pump, the semiaxis of the ellipse defining respectively one tooth of the internal toothing can be tilted if necessary toward the radial direction, thus yielding an asymmetric tooth shape and favoring one running direction of the pump toothing.
In gearwheels having involute roller toothing, a toothing system with circular tooth-root fillet is generally found in practice. Nevertheless, DE 19958670 B4 mentions, in connection with the most diverse gearwheel types, the possibility in principle of an elliptical tooth-root fillet, although it does not go into further detail in this regard. From practice it is additionally known that an elliptical tooth-root fillet can reduce the tooth-root stress that occurs during rolling movement; in such a case one semiaxis of the ellipse defining the flank profile of the toothing in the tooth-root region always lies within the symmetry plane of the tooth space.